Buggy code:
public static final ItemFlamethrower Flamethrower = ( ( ItemFlamethrower ) ( new ItemFlamethrower ( ) . setUnlocalizedName ( "Flamethrower" ) ) ) ; public static final ItemSeismicReader SeismicReader = ( ( ItemSeismicReader ) ( new ItemSeismicReader ( ) . setUnlocalizedName ( "SeismicReader" ) ) ) ; public static final Item Dictionary = new ItemDictionary ( ) . setUnlocalizedName ( "Dictionary" ) ; public static final ItemGaugeDropper GaugeDropper = ( ( ItemGaugeDropper ) ( new ItemGaugeDropper ( ) . setUnlocalizedName ( "GaugeDropper" ) ) ) ; public static final Item FilterCard = new ItemFilterCard ( ) . setUnlocalizedName ( "FilterCard" ) ; public static final Item PartTransmitter = new ItemPartTransmitter ( ) . setUnlocalizedName ( "MultipartTransmitter" ) ; public static final Item GlowPanel = new ItemGlowPanel ( ) . setUnlocalizedName ( "GlowPanel" ) ; public static final ItemScubaTank ScubaTank = ( ( ItemScubaTank ) ( new ItemScubaTank ( ) . setUnlocalizedName ( "ScubaTank" ) ) ) ; public static final ItemGasMask GasMask = ( ( ItemGasMask ) ( new ItemGasMask ( ) . setUnlocalizedName ( "GasMask" ) ) ) ; public static final ItemJetpack Jetpack = ( ( ItemJetpack ) ( new ItemJetpack ( ) . setUnlocalizedName ( "Jetpack" ) ) ) ; public static final ItemJetpack ArmoredJetpack = ( ( ItemJetpack ) ( new ItemJetpack ( ) . setUnlocalizedName ( "ArmoredJetpack" ) ) ) ; public static final Item FreeRunners = new ItemFreeRunners ( ) . setUnlocalizedName ( "FreeRunners" ) ; public static final Item Balloon = new ItemBalloon ( ) . setUnlocalizedName ( "Balloon" ) ; public static final Item Dust = new ItemDust ( ) ; public static final Item Sawdust = new ItemMekanism ( ) . setUnlocalizedName ( "Sawdust" ) ; public static final Item Salt = new ItemMekanism ( ) . setUnlocalizedName ( "Salt" ) ; public static final Item Ingot = new ItemIngot ( ) ; public static final Item Clump = new ItemClump ( ) ; public static final Item DirtyDust = new ItemDirtyDust ( ) ; public static final Item Shard = new ItemShard ( ) ; public static final Item Crystal = new ItemCrystal ( ) ; public static final Item ControlCircuit = new ItemControlCircuit ( ) ; public static void register ( ) { GameRegistry . registerItem ( MekanismItems . PartTransmitter , "PartTransmitter" ) ; GameRegistry . registerItem ( MekanismItems . ElectricBow , "ElectricBow" ) ; GameRegistry . registerItem ( MekanismItems . Dust , "Dust" ) ; GameRegistry . registerItem ( MekanismItems . Ingot , "Ingot" ) ; GameRegistry . registerItem ( MekanismItems . EnergyTablet , "EnergyTablet" ) ; GameRegistry . registerItem ( MekanismItems . SpeedUpgrade , "SpeedUpgrade" ) ; GameRegistry . registerItem ( MekanismItems . EnergyUpgrade , "EnergyUpgrade" ) ; GameRegistry . registerItem ( MekanismItems . FilterUpgrade , "FilterUpgrade" ) ; GameRegistry . registerItem ( MekanismItems . Robit , "Robit" ) ; GameRegistry . registerItem ( MekanismItems . AtomicDisassembler , "AtomicDisassembler" ) ; GameRegistry . registerItem ( MekanismItems . EnrichedAlloy , "EnrichedAlloy" ) ; GameRegistry . registerItem ( MekanismItems . ReinforcedAlloy , "ReinforcedAlloy" ) ; GameRegistry . registerItem ( MekanismItems . AtomicAlloy , "AtomicAlloy" ) ; GameRegistry . registerItem ( MekanismItems . ItemProxy , "ItemProxy" ) ; GameRegistry . registerItem ( MekanismItems . ControlCircuit , "ControlCircuit" ) ; GameRegistry . registerItem ( MekanismItems . EnrichedIron , "EnrichedIron" ) ; GameRegistry . registerItem ( MekanismItems . CompressedCarbon , "CompressedCarbon" ) ; GameRegistry . registerItem ( MekanismItems . CompressedRedstone , "CompressedRedstone" ) ; GameRegistry . registerItem ( MekanismItems . CompressedDiamond , "CompressedDiamond" ) ; GameRegistry . registerItem ( MekanismItems . CompressedObsidian , "CompressedObsidian" ) ; GameRegistry . registerItem ( MekanismItems . PortableTeleporter , "PortableTeleporter" ) ; GameRegistry . registerItem ( MekanismItems . TeleportationCore , "TeleportationCore" ) ; GameRegistry . registerItem ( MekanismItems . Clump , "Clump" ) ; GameRegistry . registerItem ( MekanismItems . DirtyDust , "DirtyDust" ) ; GameRegistry . registerItem ( MekanismItems . Configurator , "Configurator" ) ; GameRegistry . registerItem ( MekanismItems . NetworkReader , "NetworkReader" ) ; GameRegistry . registerItem ( MekanismItems . WalkieTalkie , "WalkieTalkie" ) ; GameRegistry . registerItem ( MekanismItems . Jetpack , "Jetpack" ) ; GameRegistry . registerItem ( MekanismItems . Dictionary , "Dictionary" ) ; GameRegistry . registerItem ( MekanismItems . GasMask , "GasMask" ) ; GameRegistry . registerItem ( MekanismItems . ScubaTank , "ScubaTank" ) ; GameRegistry . registerItem ( MekanismItems . Balloon , "Balloon" ) ; GameRegistry . registerItem ( MekanismItems . Shard , "Shard" ) ; GameRegistry . registerItem ( MekanismItems . ElectrolyticCore , "ElectrolyticCore" ) ; GameRegistry . registerItem ( MekanismItems . Sawdust , "Sawdust" ) ; GameRegistry . registerItem ( MekanismItems . Salt , "Salt" ) ; GameRegistry . registerItem ( MekanismItems . BrineBucket , "BrineBucket" ) ; GameRegistry . registerItem ( MekanismItems . LithiumBucket , "LithiumBucket" ) ; GameRegistry . registerItem ( MekanismItems . Crystal , "Crystal" ) ; <START_BUG> GameRegistry . registerItem ( MekanismItems . FreeRunners , "FrictionBoots" ) ; <END_BUG> GameRegistry . registerItem ( MekanismItems . ArmoredJetpack , "ArmoredJetpack" ) ; GameRegistry . registerItem ( MekanismItems . FilterCard , "FilterCard" ) ; GameRegistry . registerItem ( MekanismItems . SeismicReader , "SeismicReader" ) ; GameRegistry . registerItem ( MekanismItems . Substrate , "Substrate" ) ; GameRegistry . registerItem ( MekanismItems . Polyethene , "Polyethene" ) ; GameRegistry . registerItem ( MekanismItems . BioFuel , "BioFuel" ) ; GameRegistry . registerItem ( MekanismItems . GlowPanel , "GlowPanel" ) ; GameRegistry . registerItem ( MekanismItems . Flamethrower , "Flamethrower" ) ; GameRegistry . registerItem ( MekanismItems . GaugeDropper , "GaugeDropper" ) ; FluidContainerRegistry . registerFluidContainer ( FluidRegistry . getFluid ( "brine" ) , new net . minecraft . item . ItemStack ( MekanismItems . BrineBucket ) , EMPTY_BUCKET ) ; FluidContainerRegistry . registerFluidContainer ( FluidRegistry . getFluid ( "lithium" ) , new net . minecraft . item . ItemStack ( MekanismItems . LithiumBucket ) , EMPTY_BUCKET ) ; EVENT_BUS . register ( MekanismItems . GasMask ) ; EVENT_BUS . register ( MekanismItems . FreeRunners ) ; } }

Fix:
GameRegistry . registerItem ( MekanismItems . FreeRunners , "FreeRunners" ) ;